SSL unexpectedly stoped work in app, but open fine in browser and cert is valid

[aprivate]

SSL unexpectedly stopped working in app, but SAME LINK OPENS FINE IN BROWSER and cert is valid.

Everything was working fine for 2 years without interruptions, now
the exact error after getting webresponse during debugging is

"The request was aborted: Could not create SSL/TLS secure channel"

my code:
ServicePointManager.ServerCertificateValidationCallback = New System.Net.Security.RemoteCertificateValidationCallback(AddressOf CertificateValidation)

Try
webRequest = WebRequest.Create("https://websitename.com/update.html")
webresponse = webRequest.GetResponse() 'EXCEPTION HERE
inStream = New StreamReader(webresponse.GetResponseStream())
cr = inStream.ReadToEnd()
inStream.Close()
webresponse.Close()
Dim regMatch1 As New Regex("\d+")
cr = regMatch1.Match(cr).ToString
Catch ex As Exception
RichTextBox1.AppendText(vbCr + "Error connecting to server!" + vbCr)
End Try

Private Shared Function CertificateValidation(ByVal sender As Object, ByVal cert As X509Certificate, ByVal chain As X509Chain, ByVal [error] As System.Net.Security.SslPolicyErrors) As Boolean
If cert.Subject.Contains("OU=PositiveSSL") Then
Return True
Else
Return False
End If
End Function

[Sitten Spynne]

What version of Visual Studio/.NET are you using?

Recently there was a major change in how payment processors certify encryption, and a higher standard for SSL/TLS was adopted. This means most websites had to change to use the new standard.

Versions of .NET (and actually Windows) earlier than a certain point cannot support this version of TLS.

This blog article suggests .NET 4.6 supports it out of the box, 4.5 requires configuration, 4.0 only supports it if you've installed 4.5, and there is no way to make 3.5 or earlier support these versions of TLS, but MS chickened out and some patch for 3.5 makes it possible but isn't explained on that site.

[aprivate]

Im using 2017 COmmunity Edition/NET 4.6